This may help you with your decision: MOJO is a 50' (49'-10") all steel trawler, Beebe Design #112. She displaces about 75,000 lbs and carries 1,500 gal of fuel. She is powered with a 1989 Cummins 5.9BTA-M1 engine coupled to a ZF BW-61 transmission with a 4.67:1 ratio. She swings a 40x34 4-blade prop on a 3" ss shaft. The Cummins engine does a fine job of moving her along. At 1,600 rpm she makes 7.5 kts and burns 2.7 gph. Max speed is ~9.3 kts at about 2,100 or so. She's probably a little over-propped since the Cummins is a 2,500 rpm max engine, but I don't run her wide open so it's not an issue. I've owned her since 2000 and put about 1,000 nm per year on her.